The goal of this work is to elucidate the physiological role of the redox-sensing transcription factor, SoxR, in the antibiotic-producing bacterium, Streptomyces coelicolor. While SoxR regulates an oxidative stress response against redox-cycling agents in Escherichia coli, it does not function in a similar capacity in S. coelicolor. Two lines of evidence suggest that SoxR may instead regulate the production and/or turnover of endogenously produced antibiotics in S. coelicolor. Firstly, a soxR mutant displays differences in the timing and amount of pigmented antibiotics produced when compared with wild type. Secondly, SoxR-dependent gene expression is strictly contingent on the production of the redox-active blue-pigmented antibiotic, actinorhodin. Thus far, we have identified five SoxR targets in S. coelicolor – an ABC transporter (SCO7008), two oxidoreductases (SCO2478 and SCO4266), a monooxygenase (SCO1909) and an NAD-dependent epimerase (SCO1178). These five genes were identified bioinformatically, but more may exist. In this study we will use DNA microarray analysis to identify the complete repertoire of SoxR-regulated genes in S. coelicolor. Differential gene expression between wild type and a soxR mutant will be compared at a point in development when the bacteria are actively producing actinorhodin. We anticipate that the results from this analysis will facilitate our understanding of the role of SoxR in the antibiotic-producing S. coelicolor.